The response to stress leads to mental and physical changes that improve the ability of the organism to achieve homeostasis and increases its chance for survival. It has been postulated that dysregulation in the stress system leads to various disease states such as depression, anorexia nervosa and autoimmune disease. Corticotropin-releasing factor (CRF) is the central mediator of the stress response. Patients with clinical depression display sustained activation of the hypothalamic- pituitary-adrenal (HPA) axis that may be due to hyper-CRF secretion and such patients are considered to be subject to chronic stress. CRF has recently been shown to participate in a stress-responsive circuit between the brain and immune system. Altered regulation of central CRF and changes in the HPA axis occur in chronic inflammatory disease and infection. Cytokines from cells of the immune system cause HPA activation and have been shown to transmit information from the immune system to the nervous system. I will test the hypothesis that chronic overproduction of CRF in the central nervous system causes impaired immune function. I have developed a transgenic mouse model of chronic hyper-CRF expression 91-4). This model will be used to examine immune and nervous system interactions. This mutant mouse strain overproduces CRF in the brain and has altered HPA and behavioral parameters that parallel the stress response. Thus this animal provides a unique and powerful model for investigating the effects of prolonged CRF exposure and HPA activation. The aims of this grant are: 1) To evaluate the influence of chronic central CRF overproduction on immune function through the analysis of central CRF- overexpressing transgenic mice and 2) To determine whether expression of the metallothionein-CRF chimeric transgene is regulated by mediators known to modulate CRF expression and whether control of the endogenous CRF gene is altered in this mouse model and 3) To test whether CRF is essential for immunomodulation by the nervous system and to understand the consequences of a neuroimmune system lacking CRF, an animal model will be generated without CRF via targeted disruption of the endogenous CRF gene. These studies will test whether long term exposure to increased levels of CRF lead to sustained immunosuppression and conversely, in the absence of CRF, whether stress-induced immunosuppression fails to occur. The studies proposed here include examination of CRF expression by in situ hybridization and functional analysis of the immune system using antibody responses to antigen, NK cell cytotoxicity and T cell proliferative responses. Targeted gene disruption of the CRF gene will be accomplished using homologous recombination in embryonic stem cells.